There are many fluids that are routed from one location to another by means of a conduit. The fluids include both gases and liquids. In residential dwellings, office buildings, and manufacturing facilities the most common fluids transferred by conduit or pipe include natural or LP gas for heating or cooling, water, and liquid petroleum products, an example being fuel oil.
Safety is of major concern in using the above mentioned fluids in our homes or places of business for the modern conveniences of heating, cooling, or cooking. Serious safety hazards arise when a fluid leak in the conduit system occurs, or a piece of equipment that uses one or more of the fluids malfunctions. These leaks or malfunctions can result in accumulation of explosive concentrations of fuel gases within a structure, or toxic concentrations of carbon monoxide generated from malfunction of a gas powered appliance such as a furnace, water heater, gas dryer, or the like. Similarly, property damage occurs every day due to water leaking from a water heater, broken water line, or even a bathtub overflowing. Likewise, liquid petroleum fuel is used for heating both buildings and water. Leakage of the liquid from the fuel conduit carrying the fuel, or from the device that burns the fuel, presents a hazardous situation to individuals in the vicinity.
Currently, a variety of devices are commercially available to detect gaseous hazards such as natural gas, carbon monoxide, smoke, etc. These devices usually emit an audible alarm to warn building occupants of the danger, but do nothing to remedy the situation that caused the danger.
A number of innovations have been developed relating to devices for detecting fluid leaks and shutting off fluid flow. The following U.S. patents are representative of some of those innovations.
Shuh, in U.S. Pat. No. 2,979,939, Pottash, in U.S. Pat. No. 3,261,201, and McLean in U.S. Pat. No. 3,910,102 all describe a gasoline leak detector based on pressure changes.
A line break detection system for pipelines based on pressure drop is disclosed by Ledeen et al. in U.S. Pat. No. 4,109,512.
A leak testing apparatus that measures liquid level drop is described by Oster in U.S. Pat. No. 5,440,918.
In U.S. Pat. No. 5,542,835, Kennedy et al. describe a leak detector for plastic injection molding machines that shuts down the fluid plastic injection when air flow through a conduit is blocked by plastic material.
Makel et al., in U.S. Pat. No. 5,586,050, disclose a computerized liquid natural gas management system that includes a leak detection system with emergency warning and shut-down capabilities.
Richards, in U.S. Pat. No. 5,190,069, discloses a leak detector, based on a conductivity detector, for use in water supply systems. The device uses a solenoid to close a supply conduit valve when the conductivity detector senses a leak.
MacFadyen, in U.S. Pat. No. 5,126,934, discloses a gas distribution system that includes a leak detector connected to a shut-off valve.
Most of the above described inventions for shutting off fluid flow use a solenoid valve within the fluid conduit line as the means of stopping fluid flow. The standard solenoid valve uses the solenoid to raise or lower a plunger with attached diaphragm seal to open or close -the main port of the valve body. The solenoid valve is not a full flow type valve and presents considerable flow restriction to the fluid in the valved conduit. When used with liquids, such as water, a strainer assembly is often necessary to protect the internal diaphragm from fouling due to sediment or other foreign material in the water conduit. In addition, many state plumbing codes require that line valves controlling water supply lines within buildings must be full-port shut-off valves, or have a cross-sectional area at least as large as the smallest pipe in which the valve is installed.
Thus, there is an unmet need for a device that automatically shuts off a fluid supply line to a building or piece of equipment for safety, and to prevent property damage, upon sensing a fluid leak or otherwise dangerous condition associated with use of the fluid.